KR100536791B1 - Process for the production of ruthenium(iii) acetate solution - Google Patents

Abstract

The present invention provides a process for preparing a ruthenium (III) acetate solution, which comprises reacting ruthenium (IV) oxide with a stoichiometric amount of hydrazine reducing agent in the presence of acetic acid.

Description

PROCESS FOR THE PRODUCTION OF RUTHENIUM (III) ACETATE SOLUTION

The present invention relates to improvements in precious metal compounds. More particularly, the present invention relates to improvements in ruthenium compounds and methods for their preparation.

Ruthenium (III) acetate is used herein to determine [Ru ₃ O (OAc) ₆ (H ₂ 0) _n (AcOH) _3-n ] OAc (where n has a value from 0 to 3) and its desolvation product, ie [Ru ₃ O (OAc) ₆ ] OAc, and a term used to describe the product actually composed of ruthenium (III) acetate, an admixture with small amounts of other ruthenium acetate, oxides and / or hydroxides. Ruthenium (III) acetate, though not a bulk or commodity chemical, is commercially available as a known compound. It can be used as a starting material for other ruthenium compounds and its use has been suggested as a catalyst or catalyst precursor.

Generally accepted methods for preparing ruthenium (III) acetate include the reaction of RuCl ₃ .xH ₂ O with either acetic acid / acetic anhydride or sodium acetate in ethanol, which results in poor yield of the product, and The disadvantage is that the product is contaminated with other ruthenium species such as [Ru ₂ (OAc) ₄ Cl] and chlorine and / or sodium ions. An alternative is to react the ruthenium oxide with a mixture of acetic acid and a reducing agent such as acetaldehyde or ethanol. The latter reaction is dangerous due to the explosiveness of ruthenium oxide, although it is expected to yield high purity products. It is desirable to take other alternative methods suitable for mass production, high yield production of high purity ruthenium (III) acetate. Known methods tend to cause material contamination with impurities such as halides that can cause corrosion of plant and / or vessels, and unnecessary metallic impurities that can cause loss of selectivity during the catalytic process. Another unnecessary impurity is sulfur, a known catalyst poison.

The present invention provides a method for producing a high yield of ruthenium (III) acetate solution, which comprises reacting ruthenium (IV) oxide with a stoichiometric amount of hydrazine reducing agent in the presence of acetic acid.

The process is carried out by first treating ruthenium (IV) with ruthenium (III) by treatment with a hydrazine reducing agent in the presence of acetic acid and then heating at a reflux, preferably for a long time, for example 8-24 hours. It is preferably carried out in steps. The acetic acid reagent may be glacial acetic acid, but a water-soluble acetic acid prepared by diluting glacial acetic acid with a small amount of water is preferred, and a ruthenium (III) acetate solution of the desired acetic acid composition can be easily prepared.

The recommended hydrazine ratio is 95 to 115% of the stoichiometric requirement. The stoichiometry of the reaction requires 1 mole of hydrazine for 4 moles of ruthenium because hydrazine acts as a 4 electron reducing agent. In order to avoid significant over- or low-reduction of ruthenium (IV) species, the amount of hydrazine used is preferably as close as possible to stoichiometry. During this process, hydrazine is converted to nitrogen gas and discharged. Hydrazine is preferably used in aqueous solution, but may be used in pure liquid form or in the form of a hydrazine salt in solid or solution form. The hydrazine reducing agent may be a substituted hydrazine, for example methyl hydrazine, in which case the stoichiometry is changed. However, there is a tendency to generate unwanted byproducts from substituted hydrazines, such as methylamine, and contaminate the end product. For certain applications, the contamination may not be important.

It is believed that the reduction reaction can be described by the following equation:

_{3RuO 2 .xH 2 0 + ¾N 2} H 4 + 7AcOH → [Ru 3 O (OAc) 6 (H 2 O) 3] OAc + (2 + 3x) H 2 0 + ¾N 2

The product can be recovered, preferably in solution, by cooling the reaction mixture and removing all unreacted ruthenium (IV) oxide by filtration or centrifugation. It may be isolated in solid form by a variety of methods apparent to those skilled in the art, such as solution concentration, spray drying, or precipitation of compounds by low temperature treatment or by addition of a suitable solvent.

The present invention also provides ruthenium (III) acetate which is dissolved in aqueous acetic acid solution and contains low levels of impurities such as nitrogen (200 ppm or less), halides (50 ppm or less). The solution preferably contains up to 50 ppm sulfur and up to 100 ppm metallic impurities. Most preferably, acetic acid concentration is 40 to 80% by weight and ruthenium concentration is 4 to 8% by weight.

The hydrated ruthenium (IV) oxide itself as a starting material is a known compound, but in the present invention, it is preferably prepared by reducing the sodium ruthenic acid (VI) using alcohol. Sodium ruthenic acid (VI) is a substance of known nature.

The present invention also relates to other ruthenium carboxylates which may be prepared in a similar manner to acetate.

The invention is described by way of example only in the following working examples.

Example 1

The hydrated ruthenium (IV) oxide (43.88 g) prepared above was transferred to a 250 ml beaker, mixed well with glacial acetic acid (42.3 g), and transferred to a 250 ml round bottom flask equipped with a Teflon coated stirrer bar. The suspension was washed with an amount of glacial acetic acid (42.3 g) and then water (9.0 g). After the suspension was vigorously stirred, hydrazine (4.37 g of 15.26 wt% solution in water) was slowly added via pipette over 10 minutes. The amount of hydrazine solution used was 110% stoichiometric based on the measured ruthenium content in the reaction mixture. There was intense foaming and a gradual temperature rise of about 15 ° C. The flask was refluxed for 21 hours by heating with a Liebig condenser for reflux, at which time the reaction mixture became a dark green solution. Stirring was stopped and the flask was left to cool for 24 hours. The product was filtered through glass fiber paper with a diameter of 7 cm to give a clear, dark green product solution (141.0 g) containing 5.59% by weight of ruthenium in the form of ruthenium (III). This corresponds to a total yield of 98.5%. The product solution contained up to 50 ppm halides and up to 100 ppm nitrogen.

The process of the present invention makes it possible to produce ruthenium (III) acetate in high yield, dissolved in aqueous acetic acid solution and containing low levels of impurities such as nitrogen (200 ppm or less), halides (50 ppm or less).

Claims (6)

Reacting ruthenium (IV) oxide with a stoichiometric amount of hydrazine reducing agent in the presence of carboxylic acid, the first step of reducing ruthenium (IV) to ruthenium (III) by the reducing agent in the presence of carboxylic acid And a second step of heating the ruthenium (III) for an extended period of 8 to 24 hours. Reacting ruthenium (IV) oxide with a stoichiometric amount of substituted hydrazine reducing agent in the presence of carboxylic acid, and reducing ruthenium (IV) to ruthenium (III) by the reducing agent in the presence of carboxylic acid. A first step and a second step of heating the ruthenium (III) for an extended period of 8 to 24 hours, a method of producing a ruthenium (III) carboxylate solution. The method of claim 2, wherein the substituted hydrazine is methylhydrazine. 4. A process according to any one of claims 1 to 3, wherein said reducing agent is present in stoichiometric amounts of 95 to 115%. The process according to any one of claims 1 to 3, wherein the carboxylate is acetate and the carboxylic acid is acetic acid. 6. A process according to claim 5, wherein a solution having a ruthenium concentration of 4 to 8 wt% and an acetic acid concentration of 40 to 80 wt% is prepared.